Structure and thermal stability of Langmuir-Blodgett films of barium arachidate

Peng, J. B., Barnes, G. T., Gentle, I. R. and Foran, G. J. (2005) Structure and thermal stability of Langmuir-Blodgett films of barium arachidate. Colloids And Surfaces A-physicochemical And Engineering Aspects, 253 1-3: 65-75. doi:10.1016/j.colsurfa.2004.10.103


Author Peng, J. B.
Barnes, G. T.
Gentle, I. R.
Foran, G. J.
Title Structure and thermal stability of Langmuir-Blodgett films of barium arachidate
Journal name Colloids And Surfaces A-physicochemical And Engineering Aspects   Check publisher's open access policy
ISSN 0927-7757
Publication date 2005
Sub-type Article (original research)
DOI 10.1016/j.colsurfa.2004.10.103
Volume 253
Issue 1-3
Start page 65
End page 75
Total pages 11
Place of publication Amsterdam
Publisher Elsevier
Collection year 2005
Language eng
Subject C1
250103 Colloid and Surface Chemistry
780103 Chemical sciences
0306 Physical Chemistry (incl. Structural)
Abstract The structures of multilayer Langmuir-Blodgett films of barium arachidate before and after heat treatment have been investigated using both atomic force microscopy (AFM) and grazing incidence synchrotron X-ray diffraction (GIXD). AFM gave information on surface morphology at molecular resolution while GIXD provided quantitative details of the lattice structures of the films with their crystal symmetries and lattice constants. As-prepared films contained three coexisting structures: two triclinic structures with the molecularchains tilted by about 20degrees from the film normal and with 3 x 1 or 2 x 2 super-lattice features arising from height modulation of the molecules in the films; a rectangular structure with molecules perpendicular to the film surface. Of these, the 3 x 1 structure is dominant with a loose correlation between the bilayers. In the film plane both superstructures are commensurate with the local structures, having different oblique symmetries. The lattice constants for the 3 x 1 structure are a(s) = 3a = 13.86 Angstrom, b(s) = b = 4.31 Angstrom and gamma(s) = gamma = 82.7degrees; for the 2 x 2 structure a(s) = 2a = 16.54 Angstrom, b(s) = 2b = 9.67 Angstrom, gamma(s) = gamma = 88degrees. For the rectangular structure the lattice constants are a = 7.39 Angstrom, b = 4.96 Angstrom and gamma = 90degrees. After annealing, the 2 x 2 and rectangular structures were not observed, while the 3 x 1 structure had developed over the entire film. For the annealed films the correlation length in the film plane is about twice that in the unheated films, and in the out-of-plane direction covers two bilayers. The above lattice parameters, determined by GIXD, differed significantly from the values obtained by AFM, due possibly to distortion of the films by the scanning action of the AFM tip. (C) 2004 Published by Elsevier B.V.
Keyword Langmuir-blodgett
Cadmium Arachidate
Grazing Incidence Diffraction
Atomic Force Microscopy
Chemistry, Physical
Atomic-force Microscopy
X-ray-diffraction
Grazing-incidence Diffraction
Imaging-plate Camera
Fatty-acids
Thin-films
Focusing Monochromator
Stearic-acid
Multilayers
Molecules
Q-Index Code C1

 
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Created: Wed, 15 Aug 2007, 06:25:18 EST